Knurling machine



April 22, 1952 c. F. JONES 2,593,887

KNURLING MACHINE Filed May 21, 1949 5 Sheets-Sheet l INVENTOR.

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April 22, 1952 c. F. JONES 2,593,887

KNURLING MACHINE Filed May 21, 1949 5 Sheets-Sheet 2 INVENTOR.

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April 22, 1952 c. F. JONES KNURLING MACHINE 5 Sheets-Sheet 3 Filed May 21. 1949 INVENTOR. Cer zgzz/ f g/Enes, BY

April 22, 1952 c. F. JONES 2,593,837

KNURLING MACHINE Filed May 21. 1949 5 Sheets-Sheet 4 IN VEN TOR.

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KNURLING MACHINE Filed May 21, 1949 s Sheets-Sheet 5 IN VEN TOR. Cer z zajlfanee,

Patented Apr. 22, 1952 KNURLING MACHINE Cernyw F. Jones, Economy, Ind., assignor to Perfect Circle Corporation, Hagerstown, Ind., a corporation of Indiana Application May 21, 1949, Serial No. 94,546

8 Claims.

1 The invention relates generally to knurling machines and more particularly to a machine for knurling cylindrical articles such as pistons for internal combustion engines.

The general object of the invention is to provide a knurling machine of the foregoing character, which is easy to manipulate, which performs an accurate job of knurling on articles such as pistons, and which is readily adjusted for knurling pistons of different diameters.

Another object is to provide a novel machine for knurling articles such as internal combustion engine pistons, which is adapted to place a plurality of circumferentially extending knurled bands on the thrust faces of the skirt of the piston without distorting the piston from its normal shape, the machine being provided with means to hold the piston while the knurling. is performed so that the bands of knurling will be accurately formed.

A further object is to provide a knurling machine of the bench type, in which the knurling tool is so positioned, relative to the article being knurled, that the knurling may be fully observed by the operator during its progress and he is thus able to readily control the operation of the machine.

Other objects and advantages will become apparent from the following description, taken in connection with the accompanying drawings, wherein:

Fig. l is a perspective view of a knurling machine embodying the features of the invention.

Fig. 2 is a vertical longitudinal sectional view taken substantially on the line 2--2 of Fig. 1.

Fig. 3 is a plan view of the machine.

Fig. 4. is a view of the left-hand end of th machine as shown in Fig. 2.

Fig. 5 is a vertical sectional view taken substantially on the 1ine 55 of Fig. 1.

Fig. 6 is a vertical sectional view taken substantially on the line 6-45 of Fig. 1.

Fig. '7 is a fragmentary view of a portion of the machine as seen from the line 'l--l of Fig. 2.

The present machine is adapted for knurling cylindrical articles, particularly hollow articles, on the peripheral surface thereof. In its specific aspects, the machine is designed for knurling the skirt portions of pistons for internal combustion engines or the like. In the use of such pistons, the thrust faces of the skirt portions thereof become worn and thus are so loose in the cylinders in which they operate that piston slap occurs. Furthermore, the cylinders themselves become worn and accentuate this diificulty. It is, therefore, desirable to increase the diameter of the pistons to take up excess clearance between them and the cylinder walls to eliminate the piston slap and obtain proper operation of the piston within the cylinder. It has been found that, by knurling the thrust faces of the pistons, the metal of suchfaces can be swaged outwardly to effect a. substantial increase in the diameter of the pistons and thus eliminate the excess clearance. While such knurling may be performed on old pistons to take up the excess clearance due both to the wear on the pistons and the wear on the cylinder, it may be advantageous to knurl new pistons if they are to be placed in an old cylinder block to take up for the wear on the cylinder wall.

The knurling provides a series of lines or indentations in the metal of the piston, which are so closely spaced from each other that the metal therebetween is swaged outwardly to effect the desired increase in overall diameter of the piston. Such swaging action may effect an increase of several thousandths of an inch on each side of the piston so that considerable wear may be taken up in this manner. The knurling action also provides what may be termed an interrupted surface on the skirt of the piston, and this sort of surface has been found to operate more satisfactorily than a relatively smooth surface inthat the heat generated by friction between the piston and cylinder wall is more quickly dissipated so that there is much less chance of sending occurring. Thus, the knurling process may be advantageously applied even to new pistons for operation in new blocks to provide the desired interrupted surface.

Most pistons for internal combustion engines are not truly circular in cross section but are slightly oval or cam-shaped, having a greater diameter across the thrust faces than in a direc tion perpendicular thereto and parallel to the wrist pin bore. In knurling pistons of this character, it is, therefore, desirable to prevent any distortion of the piston so that such oval shape may be maintained. Furthermore, since the wear chiefly occurs on the thrust faces, it is these surfaces which require the increase in diameter to bring them to the desired dimension. The present machine is thus constructed to handle pistons of this type and place the knurling on the thrust faces thereof without distorting the normal shape of the piston other than to increase the diameter by the swaging action of the knurling. i

The present machine, as illustrated in the drawings, is of a type adapted to be placed on a table or bench, indicated at 20 in Fig. 1. The

V to the disc 43.

machine comprises generally a base structure 2| preferably made of cast iron and preferably provided with fiange portions l9 at its ends by which the machine may be bolted to the bench. Mounted on the base structure is a work holder in the form of a chuck 22 adapted to support a work piece, which is here illustrated as a piston for an internal combustion engine, and is indicated at A. The chuck 22 is rigidly secured to a plate 23 (see Fig. 2) rigidly secured to one end of a spindle 24 supported, with its axis horizon tal, by the base structure 2!. Preferably, the spindle 24 is mounted in a quill 25 slidably mounted in an upstanding portion 23 of the base structure 2 I.

Since knurled bands extending circumferentially of the piston are to be placed on the thrust faces thereof, it is desirable to provide for even spacing of the bands longitudinally of the piston. To this end, the quill 25 is adapted to be reciprocated by means of an indexing device, indicated generally at 27, comprising a rack 33 (see Figs. 2 and 3) rigidly secured to the quill 25. The rack is adapted to operate in a groove 3| provided in the upstanding portion 26 of the base structure to hold the quill against rotation. Meshing with the rack 33 is a pinion 32 rotatably mounted in the upstanding portion 26 and formed on the end of a shaft 33 (see Fig. 6) which has a reduced portion 34 on its front end extending forwardly from the upstanding portion 26. To hold the shaft 33 against endwise movement, a circular plate 35 is rigidly secured to the upstanding portion 25 of the base structure and abuts the shoulder on the shaft 33 formed by the reduced portion 34. Keyed to the reduced portion 34 of the shaft 33 is a sleeve 36 having a flange 31 abutting the fixed plate 35. Mounted on the sleeve and encasing the flange 3'! is a disc 43 clamped against the flange 31 by means of a knob 4| threaded on the sleeve 35.

The fixed plate carries a series of circumferentially spaced apertures 42 for reception of a pin 43 carried by the disc 40. When the end of the pin 43 is in one of the apertures 42, the shaft 33 is held against rotation and, consequently, the work piece is fixed against endwise movement. The pin 43 is slidably mounted in a sleeve 44 fixed The pin 43 is normally urged into engagement with one of the apertures 42 by means of a spring 45 mounted in the outer end of the sleeve 44 and bearing against the end of the pin 43 and against a screw 43 threaded into the end of the sleeve 44. The screw 46 also functions to secure a knob 41 to the outer end of the sleeve as. To release the pin 43 from an aperture 42, it is adapted to be drawn outwardly by means of a crosspin 50 slidably mounted in a slot 5! formed in the sleeve 43. The outer ends of the pin 53 are secured to a sleeve 52 encasing the sleeve 44 and having a flange or gripping portion 53, the sleeve 52 being slidable on the sleeve 44. Thus, to release the pin 43 from one of the apertures 42, the gripping portion 53 is manually moved outwardly, and the disc 43 may then be rotated to position the pin 43 opposite the next aperture 42 in the fixed plate 35. When the gripping portion 53 is released, the spring 45 causes the pin 43 to enter the aperture 42 and thus lock the indexing device against movement to hold the work piece in the proper position for knurling the next band. If it is desired to knurl a band on the piston which is slightly out of the normal spacing provided by the indexing device, the quill 25 may be locked in any position against longitudinal movement by means of a setscrew 54 threaded in the upstanding portion 23 of the base structure.

In knurling the thrust faces of a piston, it is desirable to limit the circumferential length of the knurled bands so that they all will be equal. For this purpose, the rotation or rocking movement of the spindle 24 is limited by means comprising, in the present instance, a collar 55 (see Figs. 2, 3 and 7) keyed to a reduced portion 55 on the end of the spindle 24 opposite the chuck 22. The collar 55 is removably secured on the reduced portion 46 by means of a knob 5'! threaded on the reduced portion 56. The collar 55 is provided with peripheral notches 63 cooperating with a bar 6| to limit the angular extent of the rocking movement of the spindle. Thus, the spindle is free to rock in either direction until an end of a notch 60 engages the bar 6!, the angular extent of the notches thus determining the extent of rocking movement of the spindle. The bar BI is mounted in the upstanding portion 23 of the base structure 2| and extends parallel to the spindle 24.

The bar 6! is of sufficient length to cooperate with the notches 60 in the collar 55 when the piston is in such longitudinal position as to have the knurled tracks placed on one thrust face thereof. When it is desired to knurl the opposite thrust face, the piston, together with the spindle 24, is moved to the right, as viewed in Fig. 2, a suflicient distance for the collar 55 to clear the end of the rod 6|. The spindle may then be completely rotated to bring the opposite thrust face thereof into position for knurling, and as soon as the spindle 24 is moved to the left to bring the piston into knurling position, the collar 55 again cooperates with the rod ill to limit the rocking movement.

The rocking movement of the spindle is preferably effected by means of a hand lever 52 (see Fig. 2) threaded into a collar 63 rotatably mounted on the plate 23 which carries the chuck 22. The hand lever 62 preferably extends upwardly, and to lock the ring 53 to the plate 23, the inner end of the lever is tapered and a tapered groove 64 is provided in the plate 23. The groove 64 is adapted to.receive the tapered end of the hand lever 62 so that when the latter is tightened therein the collar 63 is thereby clamped to the plate 23. When the spindle 24 is turned to present the second thrust face of the piston to the knurl, the hand lever 52 unthreaded sufficiently to loosen its tapered end in the groove 54. The spindle and end plate 23 thus may be rotated 180 while the handle is held .,against rotation. The hand lever 32 is then threaded inwardly to tighten its tapered end in the groove 64, thus again clamping the collar 63 to the end plate 23. When the ring 53 is unlocked from the plate 23, the former may have a tendency to rotate under the weight of the hand lever 62. If the hand lever falls toward the rear of the machine, it would be rather in For this purpose, a standard counting device is mounted on the upperv face of the upstanding portion 26 and preferably is enclosed by a casing II having an aperture 12 in its upper face through which the dials of the counter may be viewed. I

The counter I0 is adapted to be actuated each time the spindle 24 is moved to theright, as viewed in Fig. 2, to move the piston out of knurling position. Since this operation occurs twice for each piston because of the two thrust faces, the counter is actuated a half countf each time. Actuation of the counter is effected by means of a spring-pressed plunger '13 normally having its end positioned in a groove 14 in 'the'upper side of the quill 25. The groove 14 extends. to the left a predetermined distance and has a curved end 15 (see Fig. 2) which cams the plunger 13 upwardly each time the quill and spindle aremoved to the right. The plunger 13 bears against a shoulder formed on a collar 15 provided'on the counter 10 to actuate the counter mechanism. Thus, each time the spindle and quill are moved to the right far enough for the collar 55 to clear the end of the rod 6|, the counter will be actuated a half count. The spindle and quill are, of course, moved to the right in this manner when the piston is shifted to bring the knurl from one thrust face to the other. The chuck 22 has only a single wrench socket so that the spindle has to be turned to its original position to bring the socket to an accessible position. Thus, the spin clle and quill will again be moved to the right to permit removal of the piston from the chuck when the knurling of both thrust faces is completed. The counter will therebybe actuated two half counts for each piston and will thus indicate the number of pistons knurled on the machine.

From the foregoing description, it will be apparent that the piston A is rigidly held for rocking movement about its axis, while a knurling tool, here shown in the form of a roller 80, is adapted to be applied to the peripheral surface of the skirt portion of the piston and the piston is held by the chuck 22 at its end adjacent the piston ring grooves therein. Since pistons are made in a wide variety of diameters and since the chuck holds the pistons on a fixedaxis, the knurling tool 80 is adapted to be adjusted radially of the piston. Furthermore, because of the fact that pistons are not trully circular but may be slightly oval, as heretofore mentioned, the knurling roller must be freely shiftable radially of the piston to prevent distortion of the piston. At the same time, of course, must bear with sufficient pressure against the peripheral surface of'the piston to sink the ridges on the knurling roller into the metal and thereby swage themetal between the ridges outwardly to increase the diameter of the piston. To this end, the piston at the point of knurling is supported by anauxiliary support or anvil which is here shown in the form of a roller 8| adapted to engage the interior of the piston immediately inside of the point at which the knurling roller 80 engages the outer surface thereof. The pressure necessary to sink the ridges of the knurling roller into the metal is obtained by clamping the wall of the piston between the knurling roller and the anvil roller 8|. The knurling roller and anvil roller, how

ever, are carried by means which is freely shift able to permit the rollers to accommodate themselves to the oval shape of the piston without undue pressure which might distort the piston.

As shown in the drawings, the knurling roller and the anvil roller 8| are carried by a carriage 82 slidably mounted on the base structure 2| below the axis of the piston for movement transverse to said axis. In the preferred form, the carriage 82 is provided with V-shaped grooves 83 (see Figs. 1 and 2) extending along both side edges of the carriage 82 adjacent both ends thereof. Cooperating with the grooves 83 are fixed guides 84 rigidly secured to the base structure 2| with one guide at each end being laterally adjustable, as by screws 85, to take up .for wear between the carriage and guides. For convenience in effecting sliding movement of the carriage 82 to adjust the knurl 80 initially into contact with the surface of the piston, a hand lever 86 is provided. The hand lever 86 is rigidly secured to a rock shaft 81 (see Figs. 1, 3 and 4) mounted in a bracket 90 on the rear of the base structure below the rear end of the carriage 82. The rock shaft 81 carries an upstanding bifurcated lever 9| connected by a link 92 to a bifurcated boss 93 on the rear end of the carriage 82. Thus, by rocking the hand lever 86, the carriage may be shifted forwardly and rearwardly transverse to the axis a of the piston to move the knurl 80 into and out of contact with the outer surface of the piston. Adjustment of the knurl for different size pistons may thereby be readily attained. a

The knurling roller 80 is rigidly supported on the carriage 82 but is adjustable so that it may squarely engage the surface of the piston. To this end, the knurling roller is rotatably mounted on a shaft I00 (see Figs. 3 and 5) carried in a yoke IOI. The yoke IOI has a round shank portion which is adjustable about its own axis to position the axis of the knurling roller parallel to the axis of the piston. The yoke IN is carried in a tool holder I02 and a pair of setscrews I03 are mounted in the tool holder I02 to hold the shank of the yoke IOI in adjusted position. The tool holder I02 is provided with a vertically extending shank portion I04 mounted for rotative adjustment in an upright I05 extending upwardly from the upper surface of the carriage 82. The shank I04 of the tool holder is also rotatably adjustable to properly adjust the knurling roller so that its axis is parallel with the axis of the piston, and is adapted to be locked in adjusted position by means of a pair of setscrews I08 threaded in the upright I05.

The clamping pressure between the knurling roller 80 and the anvil roller 81 is, in this instance, adapted to be applied by a force exerted by the anvil roller BI. However, since the anvil roller 8| is carried by the carriage 82, such force merely brings the knurling and anvil rollerstoward each other but the carriage 82 is free to shift transversely of the axis of the piston while the knurling pressure is being exerted so that the two rollers will follow the oval shape of the piston freely without tending to distort it.

To exert the necessary clamping force between the knurling roller 80 and the anvil roller 8|, the latter is mounted for swinging movement toward and from the knurling roller 80. Such swinging movement is also utilized to release the pressure between the two rollers and to permit them to be separated a sufficient distance for removal and insertion of the wall of a piston therebetween. To this end, the anvil roller BI is rotatably mounted on a shaft I I0 (see Figs. 1, 3 and 5) carried on the end of an arm II I. The arm III is elongated and extends generally parallel to the axis of the piston so that the anvil roller 8| may be inserted into the interior of the piston from the open endthereof. The arm III has a sub stantial width in a horizontal plane so that it is extremely rigid in that direction, which is the direction of force exerted in clamping the wall of the piston between the two rollers. However, the arm H I is relatively thin and may flex vertically, inthe present instance, should the anvil roller 8| encounter abutments such as the piston pin bosses or balancing pad on the interior of the piston. If the anvil supporting arm III were rigid in a vertical direction, the extent of knurling that could be performed on the exterior surface would be limited by the extent of movement of the anvil roller within the piston. By permitting the arm [II to flex vertically, the piston may be rocked slightly farther beyond the point where such abutment occurs to extend the knurl tracks.

In some forms of pistons, circumferentially extending ribs are provided for reinforcement, particularly adjacent the lower end of the skirt of the piston. If the positioning of a knurled band on the exterior of the piston caused the anvil roller 8I to ride along one side of such a rib, there would be a tendency to force the piston endwise. While the indexing device would hold the piston against such endwise movement, the forces arising because of this action might tend to distort the piston. To avoid this, the anvil roller 8| is mounted so that it may shift endwise a limited amount relative to the knurling roller 80. Thus, the anvil roller BI is slidable on its shaft H0. When it encounters a rib or the like on the interior of a piston, it may shift to the left, as viewed in Fig. 3, so that it will be slightly out of alignment with the knurling roller 30. However, a spring I09 is mounted on the shaft I I and bears endwise against the anvil roller, tending to hold the anvil roller in radial alignment with knurling roller 80, which in most circumstances is the normal position of the two rollers.

The arm III is supported by an upright arm H2 rockably mounted on the carriage to swing the anvil roller Bl into and out of contact with the interior of the piston. In order to provide for adjustment of the anvil roller 8| so that it may ride squarely against the inner surface of the piston, particularly when there is a slight taper to such inner surface, the arm I I I is rotatably adjustable on the upper end of the arm H2. Thus, the arm HI is rigidly secured to a plate H3 underlying the arm HI and pivotally secured to the arm H2 by a pivot in H4, The arm III and plate H3 are adapted to be clamped to the arm I I2 by means of a clamping screw 1 I (see Figs. 1, 2 and 3) threaded in the arm H2 and provided with locknuts Hi5 and a clamping washer Ill. To provide an adjustable rigid abutment against swinging movement of the arm H I about its pivot H4, a screw I20 is threaded into the arm H2 and abuts against a vertically extending pin I2l mounted in the plate H3 and fitting in a notch in the arm i I i.

The arm H2 is adapted to be swung about a horizontal axis to move the anvil roller 8! toward and. from the inner surface of the piston and to exert suflicient force on the anvil roller to clamp the wall of the piston between it and the knurling roller and thus sink the ridges of the knurling roller into the metal of the piston. To this end, the arm H2 is keyed to a rock shaft I 22 extending toward the carriage 82 and jour naled in a tubular support I23 rigidly secured to the side of the carriage 82 intermediate the ends thereof. To provide space for the extension of the tube I23, the base structure 2| is provided with a gap I24. Rigidity of the carriage 82 and also the attachment of the tubular support I 23 is attained by making the carriage intermediate its ends channel shape in cross section to provide a pair of downwardly extending flange portions I25. Apertures I26 are provided in these flange portions and one of the apertur I26 is adapted to receive the inner end of the tubular support I23.

The rock shaft I22 extends inwardly through the tubular support I23 and has a reduced portion I21 at its inner end located in the space between the flange portions I25 of the carriage. To effect rocking movement of the rock shaft I22, a lever I30 i-s mounted on the reduced inner end of the rock shaft I22 with the lever connected to a power-actuated means capable of exerting sufllcien't force to clamp the piston wall between the knurling roller 80 and the anvil roller 8!. In the present instance, air pressure is utilized for this purpose.

A piston for an internal combustion engine is usually made of cast metal and the interior thereof is usually not completely machined or finished so that there are considerable irregularities and protuberances which will be encountered by the anvil roller 8i as it rolls on the interior of the piston. These irregularities obviously produce variations in thickness of the piston wall and, consequently, th spacing between the anvil roller 8| and the knurling roller 80 has to be varied while the knurling pressure is maintained. By utilizing air pressure as the source of power for exerting the clamping force between the knurling and anvil rollers, the compressible nature of air permits relative yielding movement of one of the rollers relative to the other while the pressure is maintained. Thus, the use of an air actuator, indicated generally at I 3|, for the lever I30 is particularly advantageous.

The air actuator, in the present instance, comprises a cylinder I32 (see Fig. 5) formed integrally with the carriage 82 and depending from the rear end thereof. One side of the cylinder is provided with an opening I33 through which the lever I30 extends. Within the cylinder is a piston I34 having a'slot I35 in its upper portion positioned adjacent the opening I33, and in which the end of the lever I30 is positioned. Within the slot I35 is a cross pin I36 engaged by the lever I30. Air under pressure is adapted to be admitted to the lower end of the cylinder I32 through a tube I 31 connected to a suitable source, the entrance of the air being controlled by a valve I40 (see Fig. 2) having a control handle MI (see Figs. 1 and 3). The pressure of the air is preferably regulated by means of a pressure regulator I42 having a control handle I41 mounted within the base structure i2I, and a gauge I43 is provided to indicate the pressure.

When the air under pressure is admitted to the lower end of the cylinder I 32, the piston I34 is forced upwardly, rocking the lever I30 in a clockwise direction as viewed in Fig. 5, and through the rock shaft I22, causing the anvil roller iii! to engage the inner surface of the piston with sufiicient force to effect knurling by the knurling roller 80. This pressure causes the ridges on the knurling roller to sink into the metal of the piston and,by rotating the chuck 22 by means of the hand lever 62,- a knurled band is produced onthe piston. When the diameter of the piston has been sufiiciently' increased along one band of knurling, the air pressure in the cylinder is released by the valve I40. The lever I30 is then swung counterclockwise by spring means to move the anvil roller I out of contact with the inner surface of the piston. In the present instance, the lever I30 extends forwardly from its point of connection with the reduced end I2I of the rock shaft I22 and a spring I44 bears upwardly on the front end of the lever I30 to swing it in this direction. The spring I44 is preferably supported by an L-shaped bracket I45 secured to a skirt I46 depending from the front portion of the carriage 82.

To prevent the anvil roller 8I from swinging away from the interior surface of the piston more than is necessary, a stop screw I50 is provided. The screw I50 is threaded vertically into the carriage in front of the knurling roller support to engage the front end of the lever I30 as the latter swings counterclockwise in moving the anvil roller 8| away from the work. By adjustment of the stop screw I50, the desired clearance between the anvil roller and the work may be provided. A lccknut I5I is preferably provided on the stop screw I50 to hold the latter rigidly in adjusted position.

The upper surface of the carriage 82, at its rear end, may be provided with a pair of laterally spaced ribs I53, between which a gauge (not shown) may be mounted for gauging the piston A as the latter is being knurled.

- In operation, the piston A is first mounted "in the chuck 22 with the grooved end of the piston received in the chuck jaws. Since the knurling roller 80 engages the piston at the front of the machine, the piston is so positioned in the chuck that the wrist pin hole is vertical when the hand lever 62 is in a vertical position. Such chucking of the piston is preferably performed when the chuck and spindle are in their extreme right-hand position, as viewed in Fig. 2, so that the piston is clear of the knurling roller 80 and the anvil roller 8I. The piston is then moved to the left into knurling position by releasing the index pin I43 and rotating the plate 40 by means of the knob 41. If it is desired to place a knurled band adjacent the bottom edge of the piston, the index pin 43 is permitted to enter an aperture 42 in the plate 35 adjacent that point, if this properly brings a knurled band at the desired position on the piston. However, if one of the apertures 42 is not properly positioned for this purpose, the disc 40 may be unclamped by unscrewing the knob 4| enough to release the clamping pressure. The disc 40 carrying the pin 43 may then be turned relative to the fixed plate 35 the desired amount so that, when the disc 40 is reclamped by the knob M, the pin 43 and one of the apertures 42 will be properly positioned to locate a knurled band at the desired point on the piston. Thereafter, the knurled bands are placed at intervals provided by the position of the apertures 42 in the index plate 35.

When the piston has been chucked in this manner and brought into position adjacent the knurling roller 80, the carriage is shifted rearwardly by the hand lever 86 to bring the knurling roller 80 into engagement with the surface of the piston. The control handle M! for the valve I40 is then turned to admit air to the lower end of the cylinder I32 to move the piston I34 upwardly and thus rock the lever I30. Such movement of the lever I30 forces the anvil roller BI into contact with the interior surface of the piston at a point radially inward from the point of contact of the knurling roller The force with, which the anvil roller 8| bears against the interior of the piston wall is sufiicientto sink the ridges on the knurling roller into the metal of the piston; This, of course, involves a slight relative movement between the knurling roller '80 and the piston. However, since the piston is rigidly held by the chuck against movement transverse to its axis, the carriage 82 shifts because of the pressure of the anvil roller. The carriage will alsoshift during the knurling to conform to the oval shape of a piston. V

The hand lever 62 is then rocked back and forth, the limit of motion being controlled by the rod SI and the notches 60'in the collar 55 on the end of the spindle. The hand lever maybe rocked back and forth during the knurling of each band, the number of passes of the knurling roller over the surface of the metal being determined by the extent of swaging that is desired. After placing ,the firstknurled band on one of the thrust faces of the piston, further bands at longitudinal intervals thereon may be placed by shifting the indexing mechanism as above described.

' When one thrust face is completed. the indexing device is turned to shift the piston away from the knurling roller 80, that is, to the right, as viewed in Fig. 2, to actuate the counting device 10. The hand lever 62 is then unscrewed sufficiently to release its end from the plate 23 adjacent the chuck, and the chuck is turned to bring the other thrust face of the piston into proper relation to the knurling roller 80. At this time, the hand lever 62 is screwed inwardly to resecure the ring 63 to the chuck. The indexing device is then operated to shift the piston back into knurling position and the knurling operation is repeated, but this time on the opposite thrust face of the piston. At the conclusion of the knurling on the second thrust face, the piston is then again shifted to the right to cause the second actuation of the counter I0 and register one unit thereon. The piston may then be readily removed from the chuck and replaced by another piston to be knurled.

I claim:

1. A knurling machine for knurling the external peripheral surface of a hollow cylindrical article, comprising a carriage, means mounting the carriage for sliding movement transverse to the axis of the article, a knurling tool supported by said carriage and movable into engagement with said surface by movement of said carriage, a rock shaft pivotally mounted on and extending laterally from said carriage, an anvil supporting arm mounted on said rock shaft for rocking movement therewith and carrying an anvil engageable with the inner surface of the article by rocking movement of said rock shaft, and an actuator mounted on said carriage for rocking said rock shaft. l

2. A knurling machine for knurling the external peripheral surface of a hollow cylindrical article, comprising a carriage, means mounting the carriage for sliding movement transverse to the axis of the article, a knurling tool supported by said carriage and movable into engagement with saidsurface by movement of said carriage, a rock shaft pivotally mounted on and extending laterally from said carriage, an anvil supporting arm mounted on said rock shaft for rocking movement therewith and carrying an anvil engageable with the inner surface of the article by rocking movement of said rock shaft, a lever mounted on said rock shaft, and an actuator 11 mounted on said carriage. and connected to the free end of said lever for swinging the anvil into engagement with the article.

3. A knurling machine for knurling the external peripheral surface of a hollow cylindrical article, comprising an elongated carriage, means mounting the carriage for sliding movement lengthwise thereof and transverse to the axis of the'article, a knurling tool supported by said carriage and movable into engagement with said surface by movement of said carriage, a rock shaft pivotally mounted intermediate the ends of the carriage and extending laterally therefrom, an anvil supporting arm mounted on the outer end of said rock shaftand carrying an anvil engageable with the inner surface of the article by rocking movement of said shaft, a lever mounted on the inner; end of said rock shaft, and extending lengthwise; of the carriage, and an actuator mounted on said carriage and rock shaft and carrying an anvil movable into connected to the free end of said lever for swinging the anvil into engagement with the article.

4- A kn r m c ine o k u ng t e ternalperipheral surface of a hollow cylindrical article, comprising a carria Q mean mounting e r a e or li in ovem nt ran se, to the x s of t e rti e an hav n a. pa f p c d i i s, t t s des. a nu l n tool s pported by id arria an movable nt nse ent w a d sur a e b mo em n f the rriage. a o k; af extendinglate elly rom and pivotally supported byone of said skirt portions, an anvil supporting arm mounted on the Outer end o S id ck sha t a d ca r ng a anvil engageable with the inner surface ofthe article by rocking movement of said shaft, a lever located in the space between said skirt portions and mounted on the inner end of; said rock shaft, and a pneumatic actuator mounted on one end of said carriage and connected to the free end of said lever for swinging the anvil into engagement with the article.

5. A knurling. machine for knurling the external peripheral surface of a hollow cylindricalarticle, comprising a carriage, means supporting said carriage at its ends for horizontalsliding movement, transverse to and, below the. axis of the article, a tool suppo t. extending upwardly from said carriage andcarrying a knurling tool movable into engagement, with-said surface bymovementof saidcarriage, said. carriage having a pair of spaced depending skirt portions at its side intermediate its. ends, a tubular support secured to and extending laterally from one of said skirt portions parallel to said axis, a rock shaft mounted in said tubular support, an. anvil supporting arm mounted on the. outerend, of said rock shaft and; extending upwardly therefrom, an anvil carrier mountedon the upper endof said arm and carrying an anvil engageable with the innersurface of the article by rockingmovement of said shaft, a lever mounted on theinner end of said shaft between said skirt portions, and a pneumatic cylinder mounted on and" depending from one end ofsaid carriage and having its piston connected to said lever for swinging the anvil into engagement with the article.

6. A knurling machine for knurling the external peripheral surface ofa. hollow-cylindricalarticle, comprising a carriage, means mounting said carriage for sliding movement transverse to the axis of the article, a tool supportmountedpiston, an arm extending laterally from the carengagement with the inner surface of the article by rocking movement of said rock shaft, a lever secured intermediate its ends to said rock shaft, an actuator mounted on said carriage and connected to one end of said lever for moving said anvil into engagement with said inner surface, a spring supported by said carriage and engaging the other end of said lever for moving said anvil away from said inner surface, and a stop mounted in said carriage for limiting the movement of said lever by said spring.

7. A knurling machine for knurling pistons. of the character described where the piston is mounted for rocking movement about its own axis, comprising a carrier slidably mounted for movement transverse to said axis, a tool support extending laterally from said carrier, a knurling member mounted on said tool support and en-. gageable with the outer surface of the skirt of the rier, an anvil member supported by said arm and insertable into the open end of the piston for engagement with the inner surface of the skirt, and an actuator supported by the carrier for moving one of said members toward the other to clamp the skirt therebetween and to press the knurling member into knurling relation with the skirt, the carrier being freely movable as said members follow the contour of the skirt to. avoid distortion thereof.

8. A knurling machine for knurling pistons of the character described where the piston is mounted for rocking movement about itsr own axis, comprising a carrier slidably mounted for movement; transverse tosaid axis, a tool support extending laterally from said carrier, a knurling member mounted on said tool support and engageable with the outer surface of the skirt of the piston an arm. extending laterally. from. the carrier, an anvil member supported by said arm and insertable into. the open end of the piston for engagement with the inner surface of the skirt, and a pressure fluid actuator supported by the v carrier for moving one of said members toward the other to clampthe skirttherebetween and to presstheknurling member into knurling relation with the skirt, the carrier being freely movableas; said members follow the contour of the skirt to avoid distortion thereof, the pressure fluid actuator being yieldable to permit relativeshifting of the knurling and anvil members while maintainedunder pressure to accomodate variations in thickness of the skirt of the piston.

CERNYW JONES.

REFERENCES CITED.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date,

501,547 Thomson July1 8, 11393 1,006,574 Lorenz OctQ24, 19 1 1- 1,982,209 Gary Nov. 27, 1934 2,054,182 Unke Sept. 15, 1936v 2,083,775 Carroll June 15, 1937 

